The present invention generally relates to equipment and methods for removing liquids from liquid reservoirs, for example, oil well recovery equipment and methods capable of economically removing oil from an oil field.
An oil well is typically constructed to have a tubing within one or more casings that structurally support the wellbore and seal the wellbore (other than the tubing) at the surface, typically so that the pressure of the oil within the oil field is sufficient to force oil through the tubing to the surface. As an oil field is depleted, this pressure can drop to a sufficiently low level to necessitate the use of artificial lift methods and equipment, examples of which include downhole pumps, gas lifts, and surface pump-jacks. Such measures have been referred to as “secondary recovery” methods. However, because of the costs of typical lift equipment, secondary recovery methods are pursued only if the oil field is believed to make the additional cost and effort economically viable. Wells are abandoned once production drops when even secondary recovery equipment is no longer economically practical. Even so, oil remains within the oil field and would be removed if suitable equipment and methods were available.